[1000mp] IP3 on Rob Sherwood's site

[Tod - MN]

I have found that on 10 meters as the band is fading the preamp is nice.
Otherwise, I choose to leave it off in almost all circumstances. The radio
is an FT1000MP with the INRAD If mod and the 9-1 menu set at 9 or 10
depending on the phase of the moon or something equally non-related. (Who
knows why I change the value from time to time -- not I).


Tod, KØTO
 

>-----Original Message-----
>From: 1000mp-bounces at mailman.qth.net 
>[mailto:1000mp-bounces at mailman.qth.net] On Behalf Of Chuck Lewis
>Sent: Wednesday, October 13, 2004 4:13 PM
>To: 1000mp at mailman.qth.net
>Subject: [1000mp] IP3 on Rob Sherwood's site
>
>It appears, from the superscript (b), that Rob used the preamp 
>when evaluating the Mk-V (and others). Is that everyone else's 
>interpretation? If so, it's a curious choice, because the Mk-V 
>preamp adds little; my radio is sufficiently sensitive even 
>with the preamp off ("IPO"  illuminated) and menu 9-1 reduced 
>to 9 to accommodate the Inrad If mod. I have not found it 
>necessary to use the preamp even with 10 meter signals at the 
>noise floor on a quiet band. Perceived S/N (the 'practical' 
>criterion, IMO) with the preamp off is satisfactory. Surely 
>the preamp affects IP3 adversely, right? The question is how 
>much a roofing filter would improve IP3 under the conditions 
>of a disabled preamp or additional attenuation. Even more 
>basic is the issue of why the test was conducted with the 
>preamp on, if the preamp merely provides the factory s-meter 
>settings and a market-competitive sensitivity specification. 
>The same question could be asked for other radios whose data 
>reflects their preamp enabled.
>
>I'm trying not to criticize here, just asking for some 
>rationale other than "That's the way the mfr. intended the 
>device to be used". I'm looking for someone to challenge the 
>following premise:
>    "Any overall system gain beyond that which is required to 
>hear and copy the desired signal is unnecessary and probably 
>detrimental."
>
>Anyone? Anyone?
>
>Chuck, N4NM
>(who uses his "Field" in the field, and not in the laboratory)
>
>
>
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